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System Design Feedback

solpanc Member Posts: 12
edited January 2017 in THE MAIN WALL


I worked for a company for a few years that are in middle of building a heating system. Can I get some feedback on this system. I wanted to get some thoughts on this setup. I attached pictures.

in the drawing the ports to the two tanks are not accurate i just put supplies and returns anywhere.

Thanks for your help.


  • Zman
    Zman Member Posts: 7,573
    I think there is some serious overthinking going on here.
    I see at least 3 primary/secondary lops on a system that probably does not need any. Cast iron boilers are really forgiving about flow rates.
    Not sure that this system is at risk of boiler condensation, the radiant zones may be capable of it but a smart mixing valve with outdoor reset and boiler protection would take care of that.
    I like the idea of a buffer tank, it may or may not be needed with the high mass boiler. It definitely does not need to be a 4 pipe.

    Why wouldn't you just come out of the boiler, tee off to the indirect with circulator, tee off to the heat side through a 2 pipe buffer tank, then just tee to a smart mixing valve with circ for radiant and tee to a circ and a manifold for the radiators?
    3 circulators one smart mixer like taco I series and be done with it.

    It looks like the ship has already sailed on this install.
    I would suggest that 1" copper is a little small for the near boiler piping on a boiler that big, but will probably work.
    3/4" pex is way to small for a heating load of 110k.
    I would also verify the cv rating of that mixing valve it looks like a low cv model designed for DHW. The cv should be approximately the same as the designed flow rate going through it.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein